Aerodynamic design of a natural laminar flow nacelle and the design validation by flight testing

Abstract

The laminar flow technology is one of the key technologies in aeronautics offering substantial improvements in the areas of economy and ecology. This paper describes the aerodynamic design methodology for a natural laminar flow (NLF) nacelle and the subsequent verification of the design quality by flight tests with a subsonic transport aircraft. The aerodynamic design was a contribution within the framework of a European collaborative programme to flight test a natural laminar flow nacelle. The participants in this programme were the aero-engine manufacturers Rolls-Royce and MTU as well as the Institute for Design Aerodynamics of the DLR. The nacelle manufacture was undertaken by Hurel-Dubois (UK) Ltd. and some components of instrumentation were provided and operated by the University of Oxford. The flight trials, apart from having the goal of validating the aerodynamic design of the nacelle, had the major objective of obtaining realistic experience with the operational aspects of the NLF nacelle. In the first series of flight trials, which began in September 1992, the flight test results confirmed the suitability of the aerodynamic design tools used.